Fill in the blanks with numbers, and boxes by signs, so that the expressions on both sides are equal.
(a) \(4 \times (\) \(+\) \() = 4 \times 7 + 4 \times 2\)
(b) \((\) \(+\) \() \times\) \(= 2 \times 4 + 7 \times 4\)
(c) \(13 \times (16 - 4) = 13 \times\) \(- 13 \times\)
(d) \((15 -\) \() \times\) \(=\) \(\times 2 - 9 \times\)